On Tuesday 06 March 2012 09:43 AM, Paul Walmsley wrote:
Hi Rajendra
(thanks for adding in Nilesh, added him again here)
On Tue, 6 Mar 2012, Rajendra Nayak wrote:
Yes, thats my understanding too, again based on taking to people like
Nilesh, because the documentation just doesn't mention this clearly.
The 4430 TRM is a tad bit better like you said.
I guess your confusion of IO wakeups working with EN_IO_CHAIN set to '0'
is also probably coming from the fact that the bit itself is called
*EN_IO_CHAIN* which is a completely *wrong* name for the bit, as
compared to what it does.
That bit is actually used to send a WUCLK pulse through the chain, so
you set it to '1' and wait for it to propagate through the chain, then
you set it to '0' and again wait for it to propagate through.
Okay. So to confirm: EN_IO_CHAIN doesn't enable a continuous clock, it
just controls the WUCLKIN line directly?
Right.
The control to enable/disable is at 2 levels, a global switch which is
'EN_IO' in case of OMAP3 and the one at the individual pad level.
Do you happen to know what EN_IO/GLOBAL_WUEN does? For example, if it's
0, will the I/O chain not latch in wakeup events occuring on the pads?
Yes, it wouldn't. Figure 3-74 in OMAP4430_ES2.x Public TRM vO
explains this better.
The WUEN signal to each pad (which can be used to enable IO-daisy
for the given pad) is a AND of a signal from PRCM and
one from SCM.
The signal from PRCM can be enabled by writing into
EN_IO/GLOBAL_WUEN bit.
The signal from SCM can be enabled by writing to the individual
pad registers in SCM
CONTROL.CONTROL_PADCONF_<IOpad>[14] WAKEUPENABLE0
CONTROL.CONTROL_PADCONF_<IOpad>[30] WAKEUPENABLE1.
If either one of them is not enabled the IO wakeups on the pads won't
be latched. So if EN_IO/GLOBAL_WUEN is disabled, none of the pads will
be able to generate IO wakeups.
Or does it just cause the PRCM to ignore any PRCM wakeups coming from the
I/O chain? (Or something else, heh)
You can also read this thread which has some more explanation based on
my understanding of how this works
http://www.spinics.net/lists/linux-serial/msg04480.html
I've been reading that post; it's been quite helpful.
- Paul
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